Trigger set question

[Joy chenn]

I use g4x fury to match a motocycle engine,which engine is running on crank missing tooth,and have no cam sensor.The official tutorial says this mode the ECU knows 360deg of the engine ,but the engine cycled 720deg.How can it run? The ecu only knows the engine is on tdc but how can it know it's now firing tdc or exhaust tdc?

[Adamw]

With multitooth/missing mode trigger mode and sync mode set to none (no cam sensor), then the ecu will still run in sequential, however it will only sync randomly since there is no way to know if you are on exhaust stroke or compression stroke.  So approximately 50% of start attempts the ecu will start sparking on the correct stroke and the engine will start.  And approx 50% of start attempts the ecu will start sparking 360deg out so the engine will not start.  

For your information, with motorcycle engines with no cam sensor, if you have individual throttle bodies per cylinder, then you can connect a map sensor to 1 intake port and the ecu will be able to use that to sync instead of a cam sensor.  

[Joy chenn]

Oh thanks，you mean the ecu just simply try the two stroke ,if right irun if not change to another stroke.

[Adamw]

No, sometimes it will spark on the wrong stroke and will never fire even if you crank forever.  You have to stop cranking, allow the engine to stop rotating, then try again.  Just like flipping a coin, sometimes it will land on heads, sometimes it will land on tails.

[Joy chenn]

3 hours ago, Adamw said:

With multitooth/missing mode trigger mode and sync mode set to none (no cam sensor), then the ecu will still run in sequential, however it will only sync randomly since there is no way to know if you are on exhaust stroke or compression stroke.  So approximately 50% of start attempts the ecu will start sparking on the correct stroke and the engine will start.  And approx 50% of start attempts the ecu will start sparking 360deg out so the engine will not start.  

For your information, with motorcycle engines with no cam sensor, if you have individual throttle bodies per cylinder, then you can connect a map sensor to 1 intake port and the ecu will be able to use that to sync instead of a cam sensor.  

the engine dose have ITB, and the OEM map sensor does located after throttle，i can try that 

[Adamw]

Wire the map sensor to AN Volt 1.  Make sure the calibration is correct so that it reads the same as BAP with engine not running.  Then disable fuel or ignition so it can’t start and do a trigger scope capture while cranking.  Attach the scope file here and I will help you with settings 

[Joy chenn]

4 hours ago, Adamw said:

Wire the map sensor to AN Volt 1.  Make sure the calibration is correct so that it reads the same as BAP with engine not running.  Then disable fuel or ignition so it can’t start and do a trigger scope capture while cranking.  Attach the scope file here and I will help you with settings 

Actually, i use the engine in a formula student car,the rule says the engine have to be only a throttle.Now i wondering if the throttle is on upper of the intake system,can the map drop still be used in trigger?